Variable thrust reaction motor with multiple sets injector orifices

ABSTRACT

A variable thrust fluid propellant rocket motor is provided with an injector supplied with first and second fuel and oxidizer feed lines, each line being equipped with variable flow valves. The injector is adapted to cause impingements of the first fuel and oxidizer streams on the second fuel and oxidizer streams. At low thrust levels, only the first streams are used. When higher thrust levels are required, flow of the second streams is initiated and impingement of the first streams on the second streams provides for mixing of the propellants.

United States Patent Scannell et al.

[151 3,675,425 [451 July 11, 1972 154] VARIABLE THRUST REACTION MOTORWITH MULTIPLE SETS INJECTOR ORIFICES Inventors: Paul R. Scannell,Saratoga; Phil D. Ll Fence, San Jose; Wayne '1. O'Connell, Oakland. allof Calif.

Unlted Aircraft Corporation, East Hartford, Conn.

Filed: Ju y 11, 1966 Appl. No.: 564,144

Assignee:

US. Cl. 60/3974 A, 239/404 Int. Cl "fink 9/02 Field ofseanch ..60/204,3974, 258; 239/5,

References Cited UNITED STATES PATENTS 3/ I967 Richardson er a1 ..60/258III/Ila Tinltelenberg ..60/258 Rutkowski, Jr ..60/258 Primag-Examiner-Samuel Feinberg Anomey-Steven F. Stone [57] ABSTRACT A variablethrust fluid propellant rocket motor is provided with an injectorsupplied with first and second fuel and oxidizer feed lines, each linebeing equipped with variable flow valves. The injector is adapted tocause irnpingements of the first fuel and oxidizer streams on the secondfuel and oxidizer streams. At low thrust levels, only the first streamsare used. When higher thrust levels are required, flow of the secondstreams is initiated and impingement of the first streams on the secondstreams provides for mixing of the propellants.

2CIalms,3Drawingflgures PATENTEDJUL 1 1 1912 FLOW RATE (LB/SEC) SHEET10F 2 TOTAL FLOP/ ANIFOLD SET 2 MANIFOLD SET 20 4O 6O 80 I00 PERCENTTHRUST (VACUUM) INVENTORS.

PAUL R. SCANNELL PHIL D. LA FORCE WAYNE T. O'CONNELL ATTORNEYPATENTEI'JJHLH I972 3, 675 .425

sum 2 or 2 INVENTORS,

PAUL R. SCANNELL PHIL D. LA FORCE WAYNE T. O'CQNNELL BY ,7 f; 7;,;,

ATTORNEY VARIABLE THRUST REACTION MOTOR WITH MULTIPLE SETS INJECTORORIFICES BACKGROUND OF THE INVENTION Thisinvention relates to liquidpropellant reaction motors and, more particularly, to a system forproducing variable thrust levels in liquid propellant reaction motors.

Many space and earth missions for liquid propellant rocket motorsrequire engines which are capable of operating at varying thrust levelsand several general approaches have been taken in the development ofsuch variable thrust liquid rocket motors. The most basic approach is toprovide means for varying flow rates of the propellant to the combustionchamber of a rocket motor and both variable area and fixed areainjection systems have been employed to accomplish this procedure. Withrespect to fixed area injectors, the flow rate is controlled by linethrottling with external control valves; however, injection pressuredrops become excessive in such systems and it is impossible to maintainthe necessary flow pattern when deep throttling occurs. The use ofvariable area injectors tends to overcome this particular problem tosome extent, but these systems necessarily require that the valuesurfaces used to vary the injector area are exposed to high temperaturecombustion gases which tend to erode the valve surfaces and preventpositive shutoff. Other systems, such as the use of ganged engines inwhich any desired thrust can be delivered by turning on the propernumber and size of engines have also been proposed, but such systems aregenerally bulky and heavy and are far more complex than the systemswhich vary the flow rate of the propellants to the combustion chamber.

This invention, however, provides throttling over wide thrust ranges andat the same time maintains the simplicity of the line throttlingtechnique employed with conventional fixed area injector systems. Themultiple manifold injector structure of this invention overcomes thedifficulties noted above by providing two or more sets of complete fixedarea injection manifolds for each of the fluid fuel and oxidizer. Lowthrust operation employs only one manifold set, flow through which iscontrolled by line throttling upstream of the injector. When the desiredthrust level exceeds that which can be produced by one manifold set,another manifold set is operated to provide higher thrust. If higherthrust levels than can be obtained through combined operation of bothmanifold sets is required, additional manifold systems can be employed.

It is therefore an object of this invention to provide a manifoldstructure for producing variable wide range throttling ofa fluidpropellant rocket engine.

It is another object of this invention to provide a method for producingwide range throttling of fluid propellant rocket engines.

These and other objects of this invention will be readily apparent fromthe following description with reference to the accompanying drawingswherein:

FIG. 1 is a schematic cross-sectional representation of a fluidpropellant rocket engine employing the manifold system of thisinvention;

FIG. 2 is a detailed view through a section of an injector according tothis invention; and

FIG. 3 is a curve showing the operating characteristics of a typicalrocket motor according to this invention.

DESCRIPTION OF THE INVENTION Referring now to FIG. 1, a rocket motoraccording to this invention consists of a casing I defining thecombustion zone 2 and having a thrust producing nozzle section 3 at theaft end thereof. The forward end of the casing l is provided with aninjector structure 4. Fuel manifold passages 5 and 6 and oxidizermanifold passages 7 and 8 may be machined into the injector body.Passages 5 and 7 constitute a first manifold set and passages 6 and 8constitute a second manifold set. Injector orifices 9, 10, 11 and 12communicate respectively with manifold passages 5, 6, 7 and 8. Theinjector orifices are distributed across the face in any desiredpattern, such as, for example, the duodoublet pattern; however, only oneinjection grouping is shown in FIG. 1 for reasons of clarity. Theinjector orifices are arranged for each manifold set such that they havea common impingement point 13. The oxidizer manifold 7 of the firstmanifold set is connected by pipe 14 to flow control valve I5 and theoxidizer manifold passage 8 of the second manifold is connected to flowcontrol valve I6 by pipe 17. Likewise, fuel manifold passage 5 of thefirst manifold set and fuel manifold passage 6 of the second manifoldset are connected to variable flow control valves 18 and 19 by means ofpassages 20 and 21, respectively. A source of pressurized fuel isprovided upstream of fluid flow control valves 18 and 19 and incommunication therewith by means of pipes 22 and 23. Likewise, a sourceof pressurized oxidizer is upstream of flow control valves 16 and 15 andin communication therewith by means of pipes 24 and 25. The passages 5and 7 of the fuel and oxidizer manifolds of the first set are locatedadjacent the surface of the injector face to provide for cooling of theinjector face at all thrust levels. The manifolds passages of the secondmanifold set are recessed within the body of the injector. While onlytwo manifold sets are illustrated in FIG. I, it will be readily apparentthat three, four or more manifold sets can be employed if desired toincrease the range of throttling as will be hereinafter described.

In operation of the injector system, a pressurized fuel such asunsymmetrical dimethyl hydrazine and an oxidizer such as nitrogentetroxide are provided. These materials are hypergolic and it is notnecessary to provide a separate igniter; however, it is recognized thatif the materials are non-hypergolic, a conventional igniter can beemployed. To operate the system, valves I5 and 18 are opened to provideflow of the fuel and oxidizer through passages 7 and 8 and injectorports 9 and ll. The pressurized fluids are injected into the combustionchamber and impinge at point 13 causing hypergolic ignition andcombustion of the materials. The flow of the propellants can be adjustedby control of valves 15 and 18 until the valves are completely openedand the first manifold set is operating at its maximum thrust level. Aneffective operating range for manifold set I is shown in FIG. 3. At thistime, valves 16 and 19 of the second manifold set are opened to permitadditional flow of fluid through the second manifold set throughpassages 6 and 8 and injector orifices I0 and 12 into combustion chamber2. The fluid lines flowing from injector orifices l0 and 12 also impingeat a common impingement point 13. The thrust of the engine can beincreased, as shown in FIG. 3, by opening valves 16 and 19 to theirmaximum. If additional manifold sets are provided, additional thrust canalso be obtained in a like manner.

In practice it has been found that a substantial improvement inperformance occurs when the fuel and oxidizer streams of the first andsecond manifold sets impinge near the injector face, particularly whenthe engine is operating at the intermediate thrust levels obtained withlow flow rates through the second manifold set. During this phase ofoperation the pressure drop across the injector orifices of the secondmanifold set are quite low due to the large pressure drop across theflow control valves. At this level the pressure drop across the injectororifice may not be adequate in and of itself to provide distribution andmixing of the propellants required for stable and efiicient operation.However, by causing the propellants injected from the first manifoldset, which in this thrust region undergo a substantial pressure dropacross the injector orifice, to impinge upon the propellants injectedfrom the second manifold set, sufiicient energy and momentum istransferred to produce the mixing and distribution of propellantsnecessary for stable combustion.

A specific preferred embodiment of the injector structure, according tothis invention, is shown in detail in FIG. 2. The injector body 4 has aninjector face provided with plurality of injection elements distributedthere across. The injector pattern is shown in FIG. 2 as being aduo-doublet pattern; however, other patterns could be used if desired.The injector body 4 has machined therein a plurality of channelsconstituting the various manifold chambers. The oxidizer manifold of thefirst manifold set is shown as 26 and the fuel manifold of the firstmanifold set is shown as 27. The oxidizer manifold of the secondmanifold set is shown as 28, and the fuel manifold it should berecognized, however, that the relative sizes of the various injectionelements depend upon the particular propellant system being used. inother systems the oxidizer injection elements could be smaller or of thesame size as the of the second manifold set is shown as 29. Backingplates 30, 5 fuel injection elements. 31, 32 and 33 are securel mountedwithin manifold chambers In addition to the structure already described,a fuel film Y 29, 28, 26 and 27, respectively, and provide an integralleakcoolant manifold 46 is located along the periphery of the infreemanifold chamber. The fuel and oxidizer pipes of the first J' f ody 4- AE! plate 47 provided with a plurality of manifold set, 20 and 14,communicate respectively with the Orifice-5 48 dh'ects a p y of fuelalong the Combustion if ld h b 17 d 26 h u h b ki plates 33 d chamberwall to provide a degree of cooling therefor. The fuel 32. Likewise, thefuel and oxidizer pipes 21 and 17 of the film coolant manifold 46 is influid communication with fuel second manifold set extend, respectively,through backin manifold 27 through the first manifold set fuel feeders35 la e 30 and 31 of manif ld t 2, T id proper comm. which extendthroughthe inner wall of manifold 46. Cover nication between the injectionelements and their associate Plate P with orifices encloses the mahlfold46 manifold chambers, a plurality of manifold feeders are drilled andProvldes for a p y of fuel directed along the combustion h gh inj o bod4, th e d f id f d at h chamber wall. The film coolant manifold isemployed with periphery of the injector being sealed with plugs, notshown. resp uncooled ah ahlallvely cooled Combustion Thus, manifoldfeeders 34 and 35, running parallel to the sur- Chamhef- 'i mm would beq h in face of the injector face and slightly therebelow, serve as oxffly 9 combustion chamber f h "1 idizer and fuel feeder lines respectivelyfor the first manifold mleclor P-"Q h coolant mahlfold Suitable set.Manifold feeders 34 and 3s communicate with manifold f r u pp In addmonia zone Shower typ channels 36 and 37 running perpendicular to the faceof the lhfichoh P P can be lofiiated about P p y Pflhe lhieci injectorand in communication with the interior of the to P addmohal degree ofPmiechOh for the manifold chambers 26 and 27, respectively, to providefor the chamber distribution of the fluid materials. Likewise, withrespect to EXAMPLE 1 the i g g g gg g z g z fiifi zmg g A duel manifoldinjector was installed in a rocket motor mam o as i p 8 p having aconical combustion chamber 14.6 inches long, 5.8 the face of the Inector, but at a lower level within the in ector inches in diameter atits forward end and 4 inches in di t and each of these feeders 38 and 39is likewise in communicamm H at the aft end. The exit cone half anglewas 20 Such a motor tron with manifold channels such as 40 and 41 whichare in communication with the fuel manifold chamber 29 and was tiredusing nitrogen tetroxrde as the oxrdlzer and a 5050 idizer manifoldChamber 28 respecnvely mixture of unsymmetrical dimethyl hydrazine andhydrazine A typical injection element set is outlined in the circle onas the fuel The total propellant flow rate Ranged from to FIG. 2. Eachset consists of two fuel injector elements and two 22 Pounds per Secondand Smooth trans't'ons between the oxidizer injector elements for eachmanifold set, a complete varmus thnfst was Observed h the propeufm flowinjection element set comprising eight injection elements. All ate waswhlle the motorwas firmg- The following table the elements Ora set aredrilled through the injecmr face into illustrates the results ofoneseries of runs of the above motor. communication with the appropriatefeeder channel at an The 9"" thus was measured at ambient almosphere ofangle such that they all have a common impingement point as Pf f VacuumPhrust was calculatedplercemage of previously discussed. Thus each sethas associated therewith a thrusl 'hq Table I basedfm vacuum b3515-unique impingement point. The fuel orifices 42 and oxidizer The InjectorP used had elghly q h Glut-doublets orifices 43 of the first manifoldset are shown as being smaller P Shower head and F fihh coolant lhlechohThe in size than the fuel orifices 44 and oxidizer orifices 45 ofset 2first manifold s was deslsned to be capable of p s so that a properspray pattern can be maintained at the low 45 percent Of maximum thrustand I0 operate at about a 200 psi flow rates contemplated for theoperation of the first manifold pressure drop. The second manifold setwas designed to proset. Also, the fuel injectors for each manifold setare generally vide an additional 50 percent to thrust to produce the maxsmaller in size than the oxidizer injector elements for each imum l00percent thrust when both the first and second manifold set in thisparticular design in order to maintain the manifold sets were operatingat maximum, and was designed proper flow rate balance between the flowsof the various 50 to operate at psi pressure differential. The specificdetails materials. of the injector structure are set forth in Table II.

Table l Manifold set 1 Manifold set 2 Chamber oxidizer Fuel oxidizerFuel Oxldlzer Thrust Vacuum Percent pressure, flow rate, flow rate, flowrate, flow rate, fuel ratio, measured, thrust thrust p.s.l.a. lb./sec.lb./sec. lbJsec. lbJsec. s. 01110., lbs. 23. 3 0. D92 1. 68 138. 0 504.4 34.2 1.153 1.88 300.0 740.3 58. 5 2. 62 1.716 043. 8 1,232.0 08.1 4.59 1.045 1, %0.1 2,000.0 130.4 6.16 2. 00a 1, 786.1 2,717.0 159.1 7.22 1. 95 2,220.2 a, 40s. 0 100.5 7. as 2.02 2, 350.0 3,019.0 232. 0 0.43 1. 97 a, 300. 0 6, 071. 0 233.3 0.40 2.00 3,345.0 5,086.0 273. ii5.17 1. 0a 3, 870. 0 5, B43. 0 200. 0 4. 32 1.00 4, 270. 0 6, 363. 0182. s 7. 2s 1. 01 2, 540. 0 3, 943. 0 61.2 2.00 2.07 033.0 1,706.0

TABLE II.-INIECTOR DESIGN FLOW RATES Maximum Total Coolant Shower- No.of tlow rate, Thrust, area 81; film, head, injection Manifold Ill/8B0.percent; inc percent percent holes N0. 1 fuel 3.84 50 0.0933 9. 4 11. 7242 No. 1 oxidizer 7. 68 60 0.141 0 8. B 182 N0. 2 fuel 5.46 100 0.272 00 100 No. 2 oxidizer 10. 92 100 0 379 0 0 While this invention has beendescribed with respect to a specific embodiment thereof, this embodimentis considered to be illustrative rather than limiting of the invention.Various modifications may be made without departing from the scope ofthis invention, which is limited only by the following claims, whereinwe claim:

We claim:

1. A variable thrust fluid propellant rocket motor comprising:

a. a source of a fluid fuel,

b. a source of a fluid oxidizer,

c. a combustion chamber provided with thrust producing nozzle means atthe aft end,

d. an injector in the forward end of said combustion chamber, saidinjector being provided with a multiplicity of sets of injectororifices, each set comprising first, second, third and fourth fixed areainjector orifices on the face thereof which is exposed to saidcombustion chamber, said first, second, third and fourth fixed areainjector orifices of each said set being directed to cause impingement,at a common point, of fluid emitted from each said orifice, which saidpoint is unique for each said set,

e. at least first and second oxidizer supply lines in fluidcommunicating relationship with said source of oxidizer and saidinjector,

f. at least first and second fuel supply lines in fluid communicatingrelationship with said source of fuel and said injector,

g. variable flow control means associated with each of said fuel andoxidizer supply lines for adjusting the fluid flow in each of said linesindependently to any level between full on and full off inclusive, and

h. first, second, third and fourth fluid distributing means in saidinjector providing fluid communication between said first oxidizersupply line and said first injector orifice, said first fuel supply lineand said second injector orifice, said second oxidizer supply line andsaid third injector orifice, and said second fuel supply line and saidfourth injector orifice respectively;

whereby operation of said rocket motor at varying thrust levels up to afirst predetermined maximum may be obtained by flowing fluid onlythrough said first fuel and oxidizer supply lines and operation atvarying thrust levels up to a second predetermined maximum may beobtained by flowing fluid through said second fuel and oxidizer supplylines while fluid is flowing through said first fuel and oxidizer supplylines.

2. The rocket motor of claim 1 wherein said first and second fluiddistributing means comprise, in part, passages in said injectorextending substantially parallel to and subjacent to said face thereofwhereby regenerative cooling of said injector face is obtained at allthrust levels.

I l it l

1. A variable thrust fluid propellant rocket motor comprising: a. asource of a fluid fuel, b. a source of a fluid oxidizer, c. a combustionchamber provided with thrust producing nozzle means at the aft end, d.an injector in the forward end of said combustion chamber, said injectorbeing provided with a multiplicity of sets of injector orifices, eachset comprising first, second, third and fourth fixed area injectororifices on the face thereof which is exposed to said combustionchamber, said first, second, third and fourth fixed area injectororifices of each said set being directed to cause impingement, at acommon point, of fluid emitted from each said orifice, which said pointis unique for each said set, e. at least first and second oxidizersupply lines in fluid communicating relationship with said source ofoxidizer and said injector, f. at least first and second fuel supplylines in fluid communicating relationship with said source of fuel andsaid injector, g. variable flow control means associated with each ofsaid fuel and oxidizer supply lines for adjusting the fluid flow in eachof said lines independently to any level between full on and full offinclusive, and h. first, second, third and fourth fluid distributingmeans in said injector providing fluid communication between said firstoxidizer supply line and said first injector orifice, said first fuelsupply line and said second injector orifice, said second oxidizersupply line and said third injector orifice, and said second fuel supplyline and said fourth injector orifice respectively; whereby operation ofsaid rocket motor at varying thrust levels up to a first predeterminedmaximum may be obtained by flowing fluid only through said first fueland oxidizer supply lines and operation at varying thrust levels up to asecond predetermined maximum may be obtained by flowing fluid throughsaid second fuel and oxidizer supply lines while fluid is flowingthrough said first fuel and oxidizer supply lines.
 2. The rocket motorof claim 1 wherein said first and second fluid distributing meanscomprise, in part, passages in said injector extending substantiallyparallel to and subjacent to said face thereof whereby regenerativecooling of said injector face is obtained at all thrust levels.